Continuous, categorical, and time to event cocaine use outcome variables: degree of intercorrelation and sensitivity to treatment group differences

Although a number of cocaine use variables are available for use in treatme nt outcome studies, there is little information on how strongly these varia bles are related or their relative sensitivity for detecting treatment grou p differences. Eight continuous and categorical variables of cocaine use ob tained at 6-, 12-, 18-, and 24-month follow-ups, four ec ent history variab les, and one summary measure of cocaine use over the 24-month follow-up per iod were examined. The variables were generally correlated 0.30-0.50 or gre ater. An exploratory factor analysis in which the repeated measures were av eraged across follow-up points yielded two factors, one made up of incidenc e of use variables (e.g. percent days cocaine use, monetary value of cocain e, abstinence status, time to relapse, urine toxicology) and a second consi sting of perceived severity of use variables (e.g. drug and cocaine composi tes, craving). This factor solution was supported by confirmatory factor an alyses conducted at each follow-up point. None of the variables yielded sig nificant differences between the two treatment conditions in the study, sta ndard group and individualized relapse prevention continuing care. However, monetary value of cocaine used and urine toxicology variables yielded the largest effect sizes (eta(2) = 0.020 and 0.010, respectively). (C) 2001 Els evier Science Ireland Ltd. All rights reserved.